This invention lies in the field of seismic exploration. More particularly, it lies in the field of the generation of seismic waves in the earth. Still more particularly, it is concerned with a small light weight apparatus that can be used for generating elastic waves in the earth.
In the prior art the seismic method of geophysical prospecting has utilized a number of different sources of elastic waves. One of these utilizes the detonation of a solid explosive material which is generally positioned at a considerable depth in the earth in a shot hole which is tamped with water to provide a maximum coupling of the explosive material with the earth.
In another method a mixture of explosive gases is used to fill an expansible container which rests on the earth. A first of two relatively movable parts of the container is in direct contact with the earth. The second part, which carries a large mass is on the top of the first part. When the gas which fills the space between the two parts is exploded, the first part is impulsively driven against the earth, and creates therein the elastic wave energy that is required. While the simplicity and safety of using explosive mixture of gases is a desirable one, the equipment is inconveniently large, heavy and expensive, so this method is not of wide application.
In offshore work, the explosion of a mixture of gases in a container, or a gun, open on the bottom and placed over the surface of the water, provides a detonation of the gas in the gun, which strikes the surface of the water and generates therein an elastic wave.